Hydraulic elevators cars are typically driven upwardly and downwardly by a direct acting, single stage hydraulic piston and cylinder. The cylinder, which is generally constructed of steel, is usually installed underground beneath the elevator car frame and platform.
The underground environment presents several problems. The soil and ground water surrounding the cylinder may subject the cylinder to the corrosive effects of alkalies, sulphur and salt, among other things. Also, the cylinder may present an environmental hazard by leaking hydraulic fluid into aquifers.
Various methods and devices have been used to prevent cylinder corrosion. Cylinders have been covered with tapes and other coatings. Moreover, cathodic protection utilizing a sacrificial anode or impressed current has been utilized. These approaches have achieved various degrees of relatively short-term success. However, a method for long term, i.e., greater than twenty years, corrosion protection is needed.
Some cylinders are enclosed by a PVC encasement as a means of protecting the cylinder from corrosive environments. However, a PVC encasement may leak due to damage during shipping or installation, joint seepage, pit flooding, ground movement after installation, and more.
Because of the possibility that the PVC encasement might leak, detection of any leakage into the PVC encasement may be required. Obviously, if fluid is detected within the PVC encasement, it must be removed to minimize cylinder corrosion and minimize the danger to the environment. Pumps disposed at the top of the cylinder are ineffective in removing liquid from greater depths than some cylinders require, i.e. below thirty feet. Submerging a pump would also be impractical as there is not enough space to fit a pump between the PVC encasement and the cylinder. Moreover, it would be nearly impossible to service a submerged pump. A new method and apparatus to detect and remove fluid disposed between the PVC encasement and cylinder is required.